Analytic and numerical calculations of the formation of a sulphuric acid aerosol in the upper troposphere

Analytic and numerical calculations are performed on the production of sulphuric acid aerosol in conditions of a very large nucleation event observed in the upper troposphere. The numerical results feature a growing peak in the size distribution whose magnitude is reproduced well analytically, and are consistent with the observed particle number concentration at sizes greater than 25 nm (measured dry diameter), but suggest that most of the aerosol was at unobserved smaller sizes. Because of growth and coagulation, number concentrations of the aerosol rapidly become independent of the number initially nucleated, so that conclusions as to the nucleation process, either homogeneous or ion-induced nucleation, cannot easily be drawn from existing atmospheric observations. The final concentration is very insensitive to the magnitude of the SO₂ source, but, if condensation on, and coagulation with, a remnant background aerosol occurs, such nucleation events will be cut off for source magnitudes less than a specific value. Anthropogenic emissions of SO₂ which exceed this value can produce higher aerosol number concentrations in the atmosphere with consequences for the indirect effect of aerosols on the climate.     

Development of heat-and impact-resistant coatings for main pipelines

We have developed composite layered temperature-resistant silicon-organic sandwich-type coatings with thin polyurethane silicon-organic interlayers. We used the following materials as binding components: KO 921 silicon-organic lacquer with addition of éD-20 epoxy resin for prime coat, the same lacquer with addition of PZ 1040 S polyurethane elastomer for thin soft interlayers, and only KO 921 lacquer for thick hard layers. The mineral filler represented a mixture of coal ash and omiacarb in proportion 70 / 30 mass %. We have manufactured and tested laboratory specimens with two hard layers and two interlayers as well as with three hard layers and two thin interlayers. We have established that the developed composite layered coatings exceed, in their basic characteristics, the requirements of the State Standard Committee of Ukraine and foreign normative documents for the rust protection of steel main pipelines. Our coatings possess high impact strength, heightened elasticity and adhesion strength and, as to their electrical insulating characteristics, exceed these requirements by an order of magnitude. We note the complexity of the technology of applying layered composite coatings and the necessity of its improvement. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 4, pp. 59–65, July–August, 2006.     

High-current-density subnanosecond electron beams formed in a gas-filled diode at low pressures

The formation of electron beams in a gas diode filled with various gases at low and medium pressures under the action of nanosecond voltage pulses has been studied. It is shown that subnanosecond pulses of the beam current in helium, hydrogen, neon, nitrogen, argon, methane, sulfur hexafluoride, krypton, and xenon can be obtained both at atmospheric pressure and at a pressure of several units or dozens of Torr. In particular, a beam current density above 2 kA/cm² behind the foil at a pulse duration (FWHM) of 250 ps has been obtained in helium-filled diode. On the passage from the regime of ultrashort avalanche electron beam formation to the vacuum diode regime, the beam current pulse amplitude decreases, while both the beam pulse duration (FWHM) and the pulse front width increase.     

Effect of the structure of weld metal on the pitting susceptibility of welded joints of ferritic-austenitic steel

The structure of welded joints of tubes from ferritic-austenitic steel 02Kh22N5AM3 is studied by methods of metallographic, x-ray diffraction, and electron microscopic analyses. Corrosion properties of welded joints are determined in pitting tests. The results of the study are used for developing a mode of welding and heat treatment that increases substantially the corrosion resistance of the weld metal. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 32–35, July, 2006.     

Temperature effect on the formation of a relief of diamond-like carbon coatings and its modification by ion bombardment

Diamond-like coatings (DLCs) have been obtained on a UVNIIPA-001 unit employing the method of pulse arc sputtering of a graphite target. DLCs of about 1.5 μm thick were applied onto substrates of the R6M5 steel. The relief of the coatings that were deposited using different temperature regimes has been studied. It has been established that a temperature rise of the surface of a growing DLC (condensation at a high frequency of arc pulses f) leads to the growth of films with numerous protrusions on their surface. The deposition of films at a low frequency f is more preferable to form smooth and hard DLCs under the conditions of unfiltered beam of carbon ions. The modification of the surface of diamond-like carbon coatings after their application has been investigated upon bombardment with accelerated ions of inert gas (argon) or chemically active oxygen. It has been established that the argon-ion bombardment is more preferable to smooth out the DLC relief. It has been shown that the relief of DLCs must be taken into account when measuring their microhardness, whereas the transformation of interatomic bonds in the near-surface layers after ion irradiation should be taken into consideration when analyzing the coatings by the methods whose informative depth is several monolayers.     

Formation of glass synthesized by sol-gel technology

The process of glass synthesis by the sol-gel method is studied using analysis of EPR spectra. The gelation process and formation of xerogels are considered depending on the temperature-time parameters and the type of initial components. It is established that the glass phase starts to be formed at 800°C. __________ Translated from Steklo i Keramika, No. 8, pp. 9–13, August, 2006.     

Procedure for Measuring Low Concentrations of H2 and H2S Above a Water Surface

A simple measuring procedure for low concentrations of H₂ and H₂S (at the level of ppm fractions) above the surface of water by using sensitive gas analyzers is suggested. The procedure is easily accomplished in conditions outside the laboratory (under field conditions).     

Metrological Support and Standards in the Design,Production, and Use of High-Load Weighing Machines in Russia

An analysis is presented on development, production, and use of high-capacity weighing machines in Russia in the last ten years. Aspects arising in type approval testing are considered for high-capacity weighing machines working over wide temperature ranges.     

Simulation of cup-cone fracture using the cohesive model

The cohesive model is used for the prediction of the crack path during stable crack extension in ductile materials. The problem of crack-path deviation is investigated by means of simulation of crack propagation in a round tensile bar. The respective phenomenon is known as cup-cone fracture. It is shown that the model is able to predict the failure mechanism, which consists of normal fracture in the center and combined normal/shear fracture in the so-called “shear lips” at the specimen’s rim. The damage evolution and crack path predicted by the model are presented. The effect of the normal and shear failure parameters on the crack-deflection point and several aspects of the finite element mesh are discussed.